Such a cannula is known from the U.S. patent specification 4,309,994. This patent suggests that an opening in the right atrium is made, through which a cannula with Y-shaped branches can be inserted. One branch goes into the inferior vena cava, while the other goes into the superior vena cava. In this way, blood from both venae cavae can be extract d using one cannula.
Using such a cannula, it is possible to block off or to allow access to either one of the venae cavae, along the cannula to the right atrium, so that, if desired, the right atrium can be shut off from the circulatory system of the body; this is known as total bypass and partial bypass.
Opening the right atrium results in the formation of scar tissue, which can cause heart rhythm disturbances that negatively influence the circulation.